This invention relates to a jetting tool assembly for use with a drill string, and particularly, though not exclusively, for cleaning tubular components used in drilling for gaseous or liquid hydrocarbons.
It is known to assemble a downhole valve in a drillstring, and to convey the valve to a required location in a producing formation, and then to supply drilling fluid (mud) to the working end of the drillstring via the downhole valve.
In particular, it is known from U.S. Pat. Nos. 4,889,199 and 5,499,687 to provide a downhole valve in a drillstring, and which comprises a tubular casing for mounting in the drilistring, and which allows through-flow of fluid during normal drilling operations.
There is first outlet means in the casing for discharging fluid laterally outwardly from the casing, and a sleeve slidably mounted in the casing and biased by a spring to a closed position in the casing in which the sleeve closes the first outlet means. There is also second outlet means in the sleeve for discharging fluid from the sleeve when the first and second outlet means are aligned. There is also provided a first ball (which is a large deformable ball of plastics material), which can be dropped down the drillstring i.e. launched, and which can be driven by pressure of the drilling fluid to a position of engagement with the downhole valve in order to adjust its operation. In particular, the large ball can engage the sleeve and cause it to move relative to the casing into an open position in which the first and second outlets are aligned in order to discharge fluid laterally through the casing e.g. in order to inject lost circulation material into the surrounding formation when fluid is being lost to the formation.
Furthermore, a second smaller hard ball (a deactivating ball) can then be dropped down the drillstring, and which first blocks the second outlet so that pressure on the first and second balls then increases sufficiently to drive the first (deformable) ball through the sleeve, when it is required to restore normal flow of drilling fluid through the sleeve and for allowing the return of the sleeve to the closed position (blocking communication between the first and second outlet means).
The present invention is primarily concerned with an improved version of downhole valve of the type generally disclosed in these two US patents, to provide a jetting tool assembly which is especially (though not exclusively) suitable for cleaning tubular components used in drilling for gaseous or liquid hydrocarbons.
According to the invention there is provided a jetting tool assembly for use in cleaning tubular components used in drilling for gaseous or liquid hydrocarbons in producing formations, said assembly being connectable to a hollow drillstring and having a first mode of operation which allows through-flow of fluid and lengthwise of the drillstring, and a second mode of operation which routes the fluid transversely outwardly of the drilistring, in which the assembly comprises:
a hollow main body through which axial flow of fluid can take place between an inlet end and an outlet end of the main body, in the first mode of operation;
outlet port means in the wall of the main body through which fluid can flow transversely of the drillstring in the second mode of operation;
a control sleeve slidably mounted in the main body for movement between a first position in which it blocks communication between the interior of the main body and said outlet port means, and a second position in which it allows communication between the interior of the main body and the outlet port means;
means biassing the sleeve towards said first position;
a ball receiver arrangement at one end of the sleeve to receive a ball when the latter is launched down the drillstring to activate the tool assembly, said arrangement being operative when engaged by a launched ball to move the sleeve to the second position against the biassing means;
a jetting body mounted externally on the main body; and
one or more jet outlets in the wall of the jetting body and communicating with said outlet port means so as to direct fluid outwardly against the internal wall of a surrounding tubular component for cleaning purposes when the tool assembly has been activated.
A tool assembly according to the invention may therefore be used to advantage during well xe2x80x9ccompletionsxe2x80x9d. The tubular components which may be cleaned may comprise a BOP (blow out preventer), a casing or a riser i.e. generally large diameter pipes.
Preferably, a series of cleaning jet outlets is provided in the wall of the jetting body, and arranged to direct jets of cleaning fluid radially outwardly, or outwardly at an angle as may be required.
The jetting body is mounted on the main body to form a rigid assembly, and preferably is assembled by slidable movement lengthwise of the main body to take up a required axial location on the main body, and then can be locked in position e.g. by a retainer nut.
The jetting body is therefore held captive against movement longitudinally of the main body upon assembly, but preferably it is also held against relative rotation.
Conveniently, there is a spline and groove type interfit between the main body and the jetting body, and which may be provided by a series of spline bars and respective grooves arranged at equal circumferential spaces along the interface between the outer surface of the main body and the inner face of the jetting body.
If, for example, eight splines and grooves are provided, then in the event of unacceptable excessive wear arising on any surface of the jetting body, the assembly may be released to allow slidable separation, followed by relative angular adjustment e.g. through 45xc2x0, to align the spline bars and the grooves, and slidable assembly again, but this time bringing a new surface of the jetting body to be engaged by the fluid flowing outwardly of the outlet port means in the main body.
If desired, plug inserts may be provided in the jet outlets in the wall of the jetting body to assist in unplugging any debris lodging in the jet nozzles.
A ball catcher device may be arranged below the tool assembly, to catch the balls used to activate the tool assembly, such balls being dislodged by being deformable under the action of a second, hard deactivating ball launched down the drill string, so that the sleeve returns to its first position, and the activating deformable ball (and the deactivating ball) can move lengthwise of the sleeve to be caught by the catcher device.
To prevent any balls in the catcher device from being return to the surface, a retainer flap may be provided which acts like a one way valve, to allow downward movement of the balls from the sleeve, but prevents return movement.